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-   -   tripod balancing question (http://forums.pelicanparts.com/porsche-911-technical-forum/464366-tripod-balancing-question.html)

Alan L 03-21-2009 07:07 PM

tripod balancing question
 
Read most of the threads. Still tossing up over buying/fabricating some scales. Meantime, thinking of getting it as close as I can via tripod method.
I can understand the tripod method for an unweighted (ie near neutral) car. Should I be putting weight in the drivers seat with the tripod method - since I am working off heights.
My suspicion is Yes.
But this will lower the driver side, and cause me to jack it up further - which would increase the wheel loadings on that side?
Thanks
Alan

Noel 03-22-2009 05:31 AM

I would say yes, especially depending on the driver's weight.

I used the tri-pod method and recently had it checked at my mechanic and it was very close. I'm sure you saw my comment on this in the threads you have already read.

jpnovak 03-22-2009 08:30 AM

the front tripod method is counter-intuitive. By raising the DS you shift the center of gravity to the opposite side, thus transferring load. Besides, adding weight will compress the spring on the DS to balance the increased ride height on the DS.

Alan L 03-22-2009 10:22 AM

OK.
Drivers weight in the car.
Thanks guys.
Alan

Tom '74 911 03-22-2009 11:21 AM

Quote:

Originally Posted by Alan L (Post 4559295)
Should I be putting weight in the drivers seat with the tripod method - since I am working off heights.
My suspicion is Yes.

Sarcastic answer first: The answer is dependent on whether you want your car balanced while it's sitting static in your garage, or when it's actually driving down the road (with you in it). If it were me, I'd prefer to have it set up for driving!

Sarcasm aside, I balanced mine w/out weight in the driver's seat a few years ago, then weighed it on some scales - the weights were close enough that we didn't change anything so . . . YMMV.

Tom

911st 03-22-2009 11:32 AM

Lets see. If you weigh 200 lbs about 40% will go to the front or 80 lbs. about 75% will go to the left front for 60#rf, 20#fr. That is a 40 lb differance. Front spring rate is about 110" so 40 lbs differance would make the left front deflect about .36" more with the driver.

60% of the 200lb driver weight will go to the rear or 120#. About 75% to the left and 25% to the right so 90#lr, 30#lr. Thus about 60# more to the righ rear. Stock Rear spring rate is about 122lbs per inch. Thus the left rear would deflect about .5" more than the right rear.

Thus, one migh be well served to put driver weight in.

I would measure the torsion bar height, not to the fenders.

I am not an expert and could be wrong or off about the numbers. Still, putting the weight in could make a significant differance.

:)

Elombard 03-22-2009 11:58 AM

Absolutely,

You do not corner weight using scales with out drivers weight either.

Can I ask another question?

I am ride heighting prior to the tripod and I have the front done. But the rear drivers is now 1/2 lower than the passenger. My instinct is to raise it 1/2 or so before I start the tripod.

Should I also lower the passenger front a bit? Or for the initial rough should I just work with the corner with the problem?

Alan L 03-22-2009 12:16 PM

Yes, it makes sense to want the driver weight in the car. Just seemed wrong, via height setting to go this way - still getting my head around this concept.
Am trying to source some cheap platform scales. If I find anything useful, will post here.
Alan


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